Angelic Rhoda Penmark, an eight-year-old with blonde pigtails, seems the perfect child. An excellent student, she is extraordinarily well-mannered and never looks unkempt in the party dresses she always wears. To make her shoes last longer, she thoughtfully asked to have metal plates put on the soles, and she charms her happily married parents, Kenneth and Christine, with cloyingly sweet affection. When Kenneth, an Air Force colonel, is ordered to the Pentagon for several weeks, Christine and Rhoda stay behind, watched over by Monica Breedlove, their middle-aged landlady. Beguiled by Rhoda’s quaintness and old-fashioned curtsies, childless Monica gives her many gifts, which Rhoda hoards in a “treasure box.” Only Christine is aware of Rhoda’s greediness, although Rhoda demonstrates it by turning angry and willful when another student, Claude Daigle, is awarded her private school’s gold penmanship medal that she covets. While Rhoda attends a school picnic, Christine lunches with Monica, her brother Emory and mystery writer Reginald Tasker. Their conversation about female murderers makes Christine uncomfortable, until her interest is piqued by the name of serial killer Bessie Denker. Intrigued, Monica, who is endlessly fascinated by psychology, convinces Christine to use “word association” to explore her feelings, causing Christine to recall that she always felt she was adopted, despite a happy childhood. While they are talking, a radio broadcast reports that Claude drowned in the bay during the picnic, and when Rhoda returns, she seems strangely unmoved by the tragedy. Her lack of compassion is noticed by Leroy, the half-witted, neurotic apartment building janitor who has never been fooled by Rhoda’s pretensions. A few days later, Rhoda’s teacher, Miss Fern, visits and tells Christine that Rhoda was the last to see Claude alive and was with him on the pier under which he drowned. She says Rhoda repeatedly tried to snatch away Claude’s medal and, because of her lack of fair play, is no longer welcome at the school. The conversation is interrupted by the arrival of Claude’s parents. Drunk and belligerent, Mrs. Daigle says the medal is missing, and wonders aloud about a moon-shaped injury to Claude’s head and scratches on his hands. After Miss Fern and the Daigles leave, Christine discovers the medal hidden in Rhoda’s treasure box. While questioning Rhoda about it, she remains impervious to her daughter’s attempts to manipulate her with demonstrative affection. Christine then remembers that Rhoda was bequeathed a beautiful trinket from an elderly woman who died falling down some stairs when Rhoda was alone with her. On another day, Leroy, wanting to frighten Rhoda, accuses her of killing Claude and tells her that blood traces cannot be washed off a murder weapon. Rhoda later asks Christine if this is true, thus increasing Christine’s suspicions. That evening, when Christine, pretending to write a book, asks Tasker about child murderers, he tells her that the “greatest” killers often start young and come from advantageous backgrounds. The idea of inherited criminal tendencies, he explains, is popular with many criminologists and behavioral scientists. However, Christine’s father, Richard Bravo, a highly respected journalist who is also present, nervously dismisses the “bad seed” theory as unsubstantiated. Tasker then suggests that Bessie Denker, about whom Richard wrote several articles years earlier, proves the theory, but Richard claims to have forgotten the articles. Tasker explains to Christine that Bessie’s beauty and sweet disposition convinced jurors to acquit her of three separate indictments and that some criminals, having no capacity for guilt, present “a more convincing picture of virtue than normal folk.” Tasker recalls that Bessie, who had a child, escaped to South America where she continued killing. After Tasker leaves, Christine describes her recurring dream to Richard, in which she hides from a beautiful mother who scares her. Eventually, Richard reveals that she is Bessie's daughter, and was adopted by he and his wife after she was discovered in a field at the age of two. Christine fears that Rhoda has inherited Bessie’s criminal tendencies, but Richard refuses to believe it. Later that evening, Christine catches Rhoda discarding her shoes in the incinerator chute and realizes that a steel plate made the half-moon mark on Claude’s head. After Rhoda confesses that she was responsible for Claude’s drowning, Christine, torn between justice and a mother’s love, asks Rhoda how the elderly lady fell down the stairs and Rhoda admits that she pushed her. The next day, Leroy notices that Rhoda is without her tap shoes and tricks her into admitting that she burned them in the incinerator. To torment her, he falsely claims that he retrieved them and, when she furiously demands them back, realizes that his malicious teasing has uncovered the truth about Claude’s death. Meanwhile, Monica, who is concerned about Christine’s haunted look, offers her vitamins and sleeping pills. Later, Rhoda sneaks some matches from Christine’s purse, locks Leroy in the cellar after starting a fire there and sits down at the piano to practice. Although rescued by Emory and Tasker, Leroy dies from the burns. That evening, Rhoda asks for the medal, but Christine says she dropped it into the bay at the end of the pier. Christine then gives Rhoda several sleeping pills, calling them vitamins, and after Rhoda falls asleep, tells her that she is saving her from imprisonment and other indignities. Then, Christine goes to her own room and shoots herself. Two days later, the hospitalized Christine lies comatose, while Kenneth, Emory and Monica, who saved both mother and daughter from death, ponder her attempted suicide. Although Richard guesses Christine’s motive, he says nothing. At bedtime, Rhoda tells Kenneth that she is to inherit Monica’s pet lovebird and that she and Monica will sunbathe on the roof soon. During the stormy night, Christine regains consciousness and, by phone, tells Kenneth she must pay for her “dreadful sin,” to which Kenneth says they will solve their problems together. Meanwhile, Rhoda sneaks out to search for the medal in the bay, heedless of the rain. When lightning strikes the pier, she goes up in smoke.

As noted in a 20 May 1956 LAT article, an epilogue in which cast members are identified appears immediately following “The End” title card. The voice-over announcer, producer-director Mervyn LeRoy, begins the epilogue by saying, “One moment, please…. and now, ladies and gentlemen, our wonderful cast.” All actors who were listed in the opening onscreen credits, except Frank Cady, who played “Mr. Daigle,” appear individually in a doorway of the Penmarks' apartment to take a stage bow, beginning with “Mr. Gage Clark as ‘Tasker.’” Each actor is introduced formally with his repective name as character. Actor William Hopper, whose first name is written as "William" in the opening title cards, is introduced as “Mr. Bill Hopper” during the epilogue. “Miss Patty McCormack” curtsies in the same exaggerated style as her character, followed by “Miss Nancy Kelly as ‘Christine Penmark’” who is introduced last. Kelly then enters the living room set, points to McCormack, and says, “As for you…,” then pulls the child over her knees to spank her. According to the LAT article, which also provides a brief history of screen credits, the epilogue was added to “remove some of the bad taste… left by this horrific shocker.”
Possibly, to further mollify the audience, screenwriter John Lee Mahin assured potential viewers in a Nov 1955 LAT article that the “bad seed” theory was "specious," and only important to the film because of its effect on Christine, “who is upset enough to believe anything when she discovers her daughter is a murderess.” Although several of the characters, among them, “Rhoda Penmark,” spoke with a slight southern accent, the location of the story was not made clear in the film. According to a plot synopsis found in the copyright record, the story is set in the “deep South” and Maxwell Anderson’s play states that the Penmarks live in “a suburb of a southern city.” The piano piece that “Rhoda” plays and sings and is heard as a theme throughout the film is the traditional French children’s song Au Claire de la Lune . The book Rhoda claims to have won in Sunday School, Elsie Dinsmore , was a story with religious themes about a pious eight-year-old; it was written by Martha Finley in 1867.
A 6 Nov 1955 LAT article erroneously states that Rhoda’s father was said to be dead in William March’s original novel; however, in the novel it was Christine's father, "Richard Bravo," who was dead. The character of Bravo was added to the stage play and the film, which, in general, remained very similar until the story's conclusion. In the play, Christine succeeds in killing herself, leaving her husband and "Monica Breedlove" confused about Christine’s motive and unaware of the danger posed by Rhoda. The cloying endearment, “What will you give me for a basket of hugs? I will give you a basket of kisses,” that is heard throughout the film, is spoken by Kenneth and Rhoda at the end of the play and the novel. Bravo does not appear at the end of the play, as he did in the film. In the play, during the lunch scene, the psychology fanatic Monica mentions that she believes her brother is a “larvated homosexual” and that she has a “subconscious incestuous fixation” on him. These lines do not appear in the film.
March’s novel was published in 1954. As early as 14 Dec 1954, the date of a letter to Jack L. Warner which was found in the MPAA/PCA Collection at the AMPAS Library, Geoffrey M. Shurlock of the PCA stated that “the property violated the spirit and letter of the Code.” Another letter in the collection, dated 30 Dec 1954, stated that director Billy Wilder was interested in producing the story as an independent film. According to a 15 Jan 1955 memo in the PCA file, Shurlock’s office sent letters to several studios, among them, Paramount, Columbia and Universal, even though they had not inquired about the property, to caution them against it. Despite the PCA’s objections to the film, the files indicate that Buddy Adler, Frank McCarthy and Dore Schary had expressed interest in producing the film and, according to a 28 Jan 1955 HR news item, several companies bid for the property, which Warners bought for $300,000.
An 8 Apr 1955 HR news item reported that the “deal” agreed upon was in abeyance pending the approval of the PCA and that Milton Sperling and his United States Pictures would produce the work for Warner Bros. only if the code problems were worked out. In a letter from Adler to Shurlock dated 17 Oct 1955, Adler demanded to know why another company was given approval to make the film, as he believed that he had had “the inside track” in Jan 1955, but was told in a meeting that a film about a child murderer would never receive sanction. A week letter, Shurlock wrote a response to Adler stating that, at the time, “in good faith,” the office “could not envision any treatment” that would make the property acceptable, but had retracted when signed director Mervyn LeRoy came up with a treatment that seemed to do what the office thought was impossible.
Warner Bros. production notes for the film reported that three endings were shot. According to a Nov 1955 LAT , the end of the film was kept secret and the last five pages of the script were not distributed until ready to shoot. In addition to Kelly, who won a Tony award for her performance, Evelyn Varden, Henry Jones, Joan Croyden and Eileen Heckart and ten-year-old McCormack also reprised their Broadway roles for the film. The film marked the motion picture debut of Croydon. Although Broadway actress Croydon also appeared on television, The Bad Seed may have marked her only feature film appearance.
Although onscreen credits read "and introducing Patty McCormack," McCormack had previously appeared in the 1951 film Two Gals and a Guy (see below), as well as various roles on stage and on television. A Nov 1955 HR news item adds Robert Alderett to the cast, but his appearance in the film has not been confirmed. Kelly was nominated for an Academy Award for Best Actress, but lost to Ingrid Bergman in Anastasia . Nominees McCormack and Heckart lost the Best Actress in a Supporting Role award to Dorothy Malone in Written on the Wind . Hal Rosson was also nominated for an Oscar for Achievement in Cinematography (Black and White).
A television adaptation of the story, also titled The Bad Seed , aired in 1985. That version starred Blair Brown, Lynn Redgrave and Christa Denton as Christine, Monica and Rhoda, respectively, and was directed by Paul Wendkos.

The American Film Institute is grateful to Sir Paul Getty KBE and the Sir Paul Getty KBE Estate for their dedication to the art of the moving image and their support for the AFI Catalog of Feature Films and without whose support AFI would not have been able to achieve this historical landmark in this epic scholarly endeavor.